Need suggestion

Hey, I want a suggestion. A person reached out to me,he has built a few small startups previously and wants to build an AI saas product. He is saying you will be in a higher position with around x% equity. Now I have a job in a mid level startup ( I am a fresher, 23 years old, got a job last month) . Now, what should I do ? Should I join him side by side. Or focus on my job and build my skills to grow more for the future?